The present invention relates to aircraft engine systems and, more particularly, to improved seal retention in high pressure butterfly valves.
Butterfly valves that use a piston ring type seal usually require some kind of positive retention of the seal in the seal groove. A commonly used device is a U-shaped wire which extends axially through the seal and the butterfly. The free ends are bent radially inward to keep the seal retainer in place. In the smaller butterfly valves, the wire retainer becomes fairly small in diameter, on the order of 0.030 inches, because of the narrow radial thickness of the seal. Consequently, shearing or wearing commonly causes early failure. If the retainer fails, or a retention is not used, high pressure drops can pull the seal out of the groove and jam the valve.
The current butterfly valve vane requires a two piece design with an "L" shaped seal ring to properly seal the valve. As the butterfly valve closes, there can be a high pressure differential created from the upstream side of the vane to the downstream side of the vane. This creates a force capable of pushing the seal out of the groove in the vane. Approaching the closed position, the seal begins to rub the converging wall of the housing bore, creating a friction load which can bend the seal over the edge of the seal groove and destroy the seal. A two piece butterfly vane is one way to capture the seal, providing full perimeter capture of the seal. Unfortunately, the "L" shaped seal design is expensive to manufacture, due to both the more complicated seal configuration and the need to machine two interfacing surfaces into a two piece vane.
It is therefore highly desirable and an object of the present invention to provide an improved butterfly valve seal retainer to retain the seal in the seal groove.
Another object of the present invention is to provide such a seal retainer which is capable of sustaining increased wear and load without failing.
Another object of the present invention is to provide a more cost effective means for capturing a butterfly seal for high pressure valve applications.
Another object of the present invention is to provide such a seal which has a longer seal and valve life.
These objects and other features and advantages will become more readily apparent in the following description when taken in conjunction with the appended drawings.